I've noticed the 7s in the top right box which have given me the 7s in the top left and middle middle boxes (is there any standard terminology for this shape, yet?!) I've also noticed the 4 in the bottom right and the 3 in the top right.

But what's that about the 9s in the bottom boxes? Bottom left has a 9 that doesn't help much and the others have several possibilities that don't help at all.

I have also worked out the 7/8 pairs in bottom left and right, but again they don't lead anywhere.